The invention relates to a high frequency oscillator for an integrated semiconductor circuit and use thereof.
The use of semiconductor technology in automotive engineering is on the rise. Miniaturization is permitting not only improved control and regulation techniques for engine-specific functions, but is also opening the way for new safety and driving comfort systems such as parking assistance, pre-crash and side-crash functions, blind spot detection, fill level measurements, and distance measurement. Sensory mechanisms in the vehicle—miniaturized if possible—must be provided for all controlling and regulating actions.
As a rule, for the exemplary areas of used mentioned above, contactless sensors are used, which emit a measuring beam of a particular frequency that is reflected against the object to be measured, is received again by means of a receiver unit, and is then evaluated.
For fill level measurements, there are known measuring devices in the microwave range of approximately 2 to 24 GHz, which operate either according to the FMCW principle or as pulse radar. For robust stationary use under problematic ambient conditions—for example in receptacles containing combustible materials or at high ambient temperatures—fill level sensors of this kind are designed with supporting substrates such as Teflon or RT/duroid. Short-range radar systems for motor vehicles are also known, which are used for parking assistance or as pre-crash sensors, and have a measurement frequency in the vicinity of approximately 20 GHz.
For distance measurements up to ranges of 150 m, sensors have been developed through various approaches. Ultrasonic units are very inexpensive, but are relatively imprecise for this task due to their low degree of beam focusing. Laser distance measuring devices are significantly more precise, but cannot be miniaturized at will and are very expensive. There are also known distance sensors that can be used to execute measurements in the microwave range. The sensors required for this are in fact based on semiconductor circuits, but the necessary excitation sources (oscillators) can only be installed into the semiconductor circuit later with conventional hybrid techniques. It is disadvantageous here that the miniaturization is already limited due to the difficulty in reproducing the coupling of the transmitters to the semiconductor circuit. Moreover, the oscillators subsequently installed into the semiconductor circuit require expensive adjustment. The precision of the measurements also depends, among other things, on the stability of the transmission frequency. Reference oscillators required for frequency stabilization must then also be installed and adjusted.
A subsequent installation of the oscillators also requires the provision of costly connection architecture in the semiconductor circuit, including thermocouples such as copper heat sinks. Due to their insufficient frequency stability and pronounced phase jitter at frequencies above 40 GHz, known oscillators appear to be unsuitable for use in this frequency range.